Abstract
BackgroundNatural products play a significant role in human health in relation to the prevention and treatment of inflammatory conditions. One of the plants with great medicinal potentials is Diospyros kaki which is mainly cultivated in Asian countries including Korea, Japan, and China. Astringent D. kaki is a wild species with an astringent taste until they are Ripened. kaki calyx is a traditional Korean medicine (TKM) made from the stalks of astringent D. kaki and is used in treating bed-wetting, vomiting, and hiccupping. The present study was designed to investigate the potential anti-inflammatory activities of astringent D. kaki stalks based on cultivar types and stages of maturity.MethodsThe anti-inflammatory effects of the stalk extracts of local astringent D. kaki cultivar species were evaluated on RAW 264.7 cells. Cell viability was measured using a Cell Counting Kit-8 (CCK8) method. The anti-inflammatory effects were determined by measuring the nitric oxide (NO) concentration of the supernatant. Cellular signaling pathways were determined by quantitative polymerase chain reactions of inducible nitric oxide synthase (iNOS). Protein expression of iNOS and phospho-p65 was determined using western blot, and the nuclear localization of p65 was determined using confocal imaging in RAW 264.7 cells.ResultsWe found that the stage 1 (8–9 month) samples all showed a high percentage of tannic acid content and Gojongsi (Hamyang) stalks had the highest content. The stage 1 samples also showed the highest inhibition of NO production. Decreases in the expression of iNOS and phosphorylated p65, and in the nuclear localization of p65, were dose-dependent. All the extracts were nontoxic under 100 μg/ml concentration.ConclusionThis study provides insight into the changes in tannic acid content in astringent D. kaki and their anti-inflammatory effects, in relation to their stage of maturity. These results are expected to be useful in the verification of the efficacy of oriental medicine and the timing of proper harvest for medical use.
Highlights
Natural products play a significant role in human health in relation to the prevention and treatment of inflammatory conditions
The high-performance liquid chromatography (HPLC) analysis of the contents of tannic acid in relation to maturity showed that tannic acid content was higher in the immature astringent D. kaki than in the mature or dried ones (Fig. 2)
The content of tannic acid tended to decrease according to the degree of ripeness, with the immature D. kaki stalks having highest tannic acid concentration and the least found in the dried stalks
Summary
Natural products play a significant role in human health in relation to the prevention and treatment of inflammatory conditions. Inflammation is one of the major factors for the progression of numerous chronic diseases and disorders including diabetes, cardiovascular diseases, cancer, arthritis, obesity, autoimmune diseases, and as well as inflammatory bowel disease [1] It involves various cells and cytokines, which provide an initial defense after infection or tissue damage by limiting damage to the affected site [2]. The anti- inflammatory potential of plants are attributed to the presence of secondary metabolites such as saponins, glycosides, and phenolic compounds including tannins and flavonoids [9]. These phytochemicals such as tannin which is a phenol compound has various physiological functions such as antimutagenic and anti-cancer effects [10, 11]. A study by Robbins et al, [14] reported that tannins are one of the secondary metabolites that plants use in defensive mechanisms against large herbivores
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